The Official Web Site of Carlos Santana

Santana's "Smooth",featuring Rob Thomas, is the No. 2 most popular
Billboard single of all time, followed by Bobby Darin's "Mack the
Knife," Leann Rime's "How Do I Live" and "The Macarena" by Los Del Rio.
Of all the No. 1 songs in the 50 years of the Billboard Hot 100 chart,
Checker's "The Twist" ranks as the most popular single.

The Billboard Hot 100 chart measures airplay and sales information (and more recently digital downloads) in determining the nation's most popular songs. To determine the most popular song of the Hot 100 era, Billboard used a formula to determine the top song-not always relying on weeks at No. 1 since the data was reported differently in its early days.

Initially, Billboard relied on stations to report the most popular songs, and got sales surveys from record stores. But Mayfield said stations often stopped reporting on a song's popularity if it was no longer a priority for record labels. And in 1991, Billboard began relying on sales data from Nielsen SoundScan and airplay data from Nielsen Broadcast Data Systems. So Billboard weighted certain songs from different eras to make sure all songs were on an even playing field.